JP2007190804A - Original lithographic printing plate and platemaking method for lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a platemaking method for a lithographic printing plate, which shows extremely high workability even in a bright room without generation of a highly concentrated spent liquid, and especially, excellent stain resistance from a viewpoint of printability and further, the advantage to dispense with the use of a noxious solvent etc. to a human body in a platemaking work. <P>SOLUTION: In the lithographic printing plate with a hydrophilic layer formed on a support, an original lithographic printing plate is used which has the hydrophilic layer containing an inorganic pigment with 1 μm or less average particle diameter. Further, the hydrophilic layer can be continuously paired with at least another hydrophilic layer, and one of these two hydrophilic layers close to the support shows a lower inorganic pigment/binder ratio than the other far from the support. In addition, especially, an ink composition containing an aqueous ultraviolet-curable resin, is used for printing with an inkjet printer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printing plate used for lithographic printing, which can obtain an image having high resolution, does not require a handling and processing solution in a bright room, and has a particularly low manufacturing cost. .

  With the recent development of computers and peripheral devices, a planographic printing plate making method using various digital printers has been proposed. Such a lithographic printing plate is made by a dry electrophotographic laser printer due to the difference in the image portion forming method (JP-A-6-138719, JP-A-6-250424, JP-A-7- 1847, etc.), plate making using an on-demand ink jet printer using hot-melt ink (Japanese Patent Laid-Open No. 9-58144), plate making by printing an oleophilic substance or an image fixing material using an ink jet printer Without using a thermal laser or an ink ribbon (Japanese Unexamined Patent Publication No. 56-105960, Japanese Unexamined Patent Publication No. 8-295683, etc.), making a plate with a thermal printer using a thermal transfer ink ribbon (Japanese Unexamined Patent Publication No. 63-166590) There is one that makes a plate with a thermal printer (Japanese Patent No. 3522450).

  Unlike the conventional plate-making method of a lithographic printing plate in which a silver halide photosensitive material or a photosensitive resin is applied to a water retention-providing surface, the plate-making method using the above-mentioned various digital printers has no restrictions on safety light in handling, and the image There is an advantage that a lithographic printing plate can be easily and easily made in that no development treatment with an aqueous developer after recording is required.

  Among the plate making methods using the various digital printers described above, the plate making method using an ink jet printer can print with higher definition than other methods due to the recent development of ink jet printers and can be expected to be a high quality and low cost plate making method. .

  However, when trying to make a plate with an ink jet printer using an ink composition containing a substance that precipitates upon drying, the ink composition is dried and solidified during or after printing, and the head of the ink jet printer is packed. Have the problem of For example, in Japanese Patent Application Laid-Open No. 2004-66816, an aqueous colloidal dispersion is used as an ink composition. However, since such a colloidal dispersion is solidified by drying of moisture, it is very easy to pack an ink jet printer head.

  When using an on-demand inkjet printer that uses hot-melt ink, this problem does not exist because the ink becomes liquid when printing, but there is a problem that requires a special mechanism in the printer head. ing. Furthermore, it can exist as a liquid until the ink composition exits the head, but since it cools from the moment it exits the head and becomes a solid or highly viscous liquid, the ink composition is only on the lithographic printing plate precursor. As a result, the image quality is deteriorated and it is difficult to obtain a sufficient printing durability.

  For example, JP-A-56-105960 (Patent Document 1) and JP-A-2005-144692 (Patent Document 2) have also proposed plate making methods for inkjet printers using an ultraviolet curable resin as an ink composition. Since the ultraviolet curable resin is a liquid until it is exposed to ultraviolet rays, it does not clog the head of the ink jet printer and is a very preferable method. However, due to the property that the ultraviolet curable resin is a liquid until it is irradiated with ultraviolet rays, if the ultraviolet rays are not irradiated immediately after printing, bleeding occurs in the image and the image quality is deteriorated. In order to solve this problem, UV ink jet printers usually have an ultraviolet lamp installed beside the printer head, as proposed in, for example, Japanese Patent Application Laid-Open No. 2004-322560. A mechanism that suppresses heat generation is required, and a head with a very special structure is required. Accordingly, there has been a demand for the development of a system that does not cause blurring of images without using such a special head.

  It is difficult to increase the viscosity of the ink composition because of its characteristics. It is difficult to adjust to the required low viscosity with an ultraviolet curable resin alone, and the viscosity is adjusted by mixing a reactive diluent or a solvent. However, these reaction diluents and solvents are harmful to the human body. In recent years, in response to this problem, water-based ultraviolet curable resins have been developed and used in various applications. On the other hand, water-based ultraviolet curable resins have a drawback that their hardness is weaker than non-aqueous ultraviolet curable resins. For this reason, when a lithographic printing plate is made using a water-based ultraviolet curable resin, it is difficult to obtain a sufficient printing durability. Water-based UV curable resins can use water that is harmless to the human body as a diluent, but due to the lack of printing durability due to this lack of hardness, plate making methods for lithographic printing plates using this have not yet been proposed. Not.

  Numerous patents have been submitted for ink jet recording paper, and there are also many proposals for a layer structure for absorbing the ink composition more quickly. For example, in Japanese Patent Application Laid-Open No. 2004-25836 (Patent Document 3), A method has been proposed in which an ink receiving layer made of an inorganic pigment and a binding material is provided on an undercoat layer made of a binding material to improve the adhesion. The quality required for these inkjet recording papers is to quickly absorb the ink composition and quickly fix the pigments and pigments in the ink composition. For example, when the printed ink composition performs lithographic printing. The required quality of a lithographic printing plate, such as having sufficient ink acceptability, or having sufficient adhesive strength between the lithographic printing plate precursor and the ink composition and sufficient printing durability, is absolutely Is different.

In direct-drawing lithographic printing plates, many attempts have been made to increase the printing performance by changing the ratio of the inorganic pigment and the hydrophilic binder. A method has been proposed in which an inorganic pigment having a small particle diameter is contained in the surface layer and a large-size inorganic pigment is contained in the undercoat layer to improve the printing durability and stain resistance. In these direct-drawing lithographic printing plates, the image portion is composed of toner, a transfer product from a thermal transfer ink ribbon, etc., but this image component has a viscosity of about several mPa · s for forming the image portion of the present invention. Unlike an ink composition, even a solid or liquid has a very high viscosity and has almost no fluidity. Therefore, in Patent Document 3 and the like, no consideration is given to the problem of blurring of an image that occurs specifically when a low-viscosity image component of about several mPa · s is used. Could not be resolved.
JP 56-105960 A (first page) Japanese Patent Laying-Open No. 2005-144692 (first page) JP 2004-25836 A (first page) International Publication No. 01-045959 (1st page)

  An object of the present invention is to make the lithographic printing plate making technology, without generating waste liquid, extremely excellent workability in a bright room, and with high print quality with no blurring in printability, An object of the present invention is to provide a plate making method of a planographic printing plate having soiling properties. It is also an object of the present invention to provide a method for making a lithographic printing plate that does not use a solvent harmful to the human body during plate making operations.

The above object of the present invention has been achieved by the following invention as a result of intensive studies.
1) In a lithographic printing plate comprising a hydrophilic layer provided on a support, the hydrophilic layer has at least two continuous layers, and the hydrophilic layer contains an inorganic pigment having an average particle size of 1 μm or less, and the support A lithographic printing plate precursor is used, characterized in that the inorganic pigment / binder ratio of the layer close to is smaller than that of the layer far from the support.
2) The lithographic printing plate precursor as described in 1) above, wherein the inorganic pigment / binder ratio of the hydrophilic layer far from the support is 2/1 or more.
3) The lithographic printing plate precursor as described in 1) or 2) above, wherein the coating amount of the hydrophilic layer far from the support is 0.5 g / m 2 or less in terms of solid content.
4) The lithographic printing plate precursor as described in any one of 1) to 3) above, wherein the hydrophilic pigment closer to the support has an inorganic pigment / binder ratio of 1/1 or more.
5) A lithographic printing plate making method comprising printing an ink composition containing a lipophilic substance by an inkjet method on the lithographic printing plate precursor as described in any one of 1) to 4).
6) The method for making a lithographic printing plate as described in 5) above, wherein the lipophilic substance is ultraviolet curable.
7) The plate making method of a lithographic printing plate as described in 5) or 6) above, wherein the ink composition contains water or ethyl alcohol.

  According to the present invention, there is provided a lithographic printing plate that is excellent in workability in a bright room with no generation of waste liquid in the lithographic printing plate making technology and that is particularly excellent in stain resistance in terms of printability. It becomes possible. Furthermore, it becomes possible to make a lithographic printing plate without using a solvent harmful to the human body during plate making work.

  The lithographic printing plate in the present invention has a hydrophilic layer composed of two layers, and the hydrophilic layer far from the support (hereinafter referred to as the surface hydrophilic layer) contains a lot of inorganic pigments, and as a result, becomes a porous layer. In addition, the hydrophilic layer close to the underlying support (hereinafter referred to as the middle hydrophilic layer) is relatively low in pigment ratio and slightly porous. Furthermore, according to the careful experiment of the present inventor, not only the volume of the “pores” of the hydrophilic layer far from the support is large, but the diameter is large, and conversely, the average of the pores of the hydrophilic layer close to the support We found that the diameter was reduced. In the case of using the most preferable water-based ultraviolet curable resin as the ink composition, the ink is a low-viscosity solution that can be printed with an ink jet printer by diluting the high-viscosity ultraviolet curable resin with water or alcohols. When such an ink composition is driven into the lithographic printing plate precursor according to the present invention, a layer having large pores quickly absorbs the ink composition, and further, a diluent having a small molecule has a hydrophilic property with small pores below it. Although it is absorbed by the layer, it has a high viscosity, which is due to the large molecular size, but the UV curable resin cannot enter the hydrophilic layer with small pores and stays in the same position. It will be. Although the diluent in the ink composition is reduced, as a result, the viscosity of the ink composition approaches the viscosity of the UV curable resin itself and becomes a high viscosity solution, so that further movement is almost impossible and a little time after printing. Even after the lapse of time, the blur becomes very difficult to occur. Moreover, since the ultraviolet curable resin which receives ink exists in the surface side layer, it can have sufficient acceptability. Even more surprisingly, even if a low-hardness water-based UV curable resin is used, the UV curable resin embeds and cures the binder and inorganic pigment of the hydrophilic layer, so that it becomes a skeleton and high strength can be obtained. As a result, the present inventor has found that sufficient printing durability can be obtained. Therefore, in the present invention, it is important to control the size and volume of the pores, which can be achieved by keeping the size of the inorganic pigment and the ratio of the inorganic pigment / hydrophilic polymer within a preferable range. As a result, the present invention has been achieved. Details of the present invention will be described below.

  In the present invention, the hydrophilic layer means a layer containing at least one kind of hydrophilic polymer or a hydrophilic inorganic pigment such as silica or alumina. In the lithographic printing plate precursor according to the invention, a hydrophilic layer is provided on a support, and the hydrophilic layer is further divided into at least two layers. In order to achieve the object of the present invention, these hydrophilic layers must be provided continuously. In the present invention, a hydrophilic layer can be provided in addition to this. However, in order to achieve the object of the present invention, the relationship between the surface hydrophilic layer and the subsequent intermediate hydrophilic layer is important. Describe first.

  In the present invention, both the hydrophilic surface layer and the intermediate hydrophilic layer contain a hydrophilic polymer and an inorganic pigment.

  As the binder that can be used for both hydrophilic layers in the present invention, various known hydrophilic polymers can be used. Specific examples thereof include kappa type, iota type, lambda type carrageenan, fucoidan, porphyran, chondroitin sulfate, dermatan sulfate, keratan, hyaluronic sulfate, dextran sulfate, polyvinyl sulfate, and sulfuric acid described in JP-A-2005-120068. Chitosan or sodium salts, potassium salts, rubidium salts, etc. of these hydrophilic polymers, starches, seaweed mannan, agar, sodium alginate, mannan, pectin, tragacanth gum, caraya gum, xanthine gum, guar bin gum, roast bin gum, gum arabic Microbial mucilages such as homopolysaccharides such as dextran, glucan, xanthan gum and levan, heteropolysaccharides such as succinoglucan, pullulan, curdlan and xanthan gum, glue, gelatin, Proteins such as zein and collagen, chitin and derivatives thereof. Cellulose derivatives, modified gums such as carboxymethyl guar gum, cultured starches such as dextrin, processed starches such as oxidized starches, esterified starches, and the like. Synthetic products include polyvinyl alcohol, partially acetalized polyvinyl alcohol, allyl-modified polyvinyl alcohol, modified polyvinyl alcohol such as polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl isobutyl ether, polyacrylate, polyacrylic ester partial saponified product, poly Polyacrylic acid derivatives and polymethacrylic acid derivatives such as methacrylate and polyacrylamide, polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, vinyl pyrrolidone / vinyl acetate copolymer, carboxyvinyl polymer, styrene / maleic acid copolymer And styrene / crotonic acid copolymer. Among these, a hydrophilic polymer having a hydroxyl group and a sulfate thereof is preferable, and further, carrageenan is used because it has good adhesion to an ultraviolet curable resin and is easy to apply because it has setability. It is preferable. The molecular weight of the preferred hydrophilic polymer is not particularly defined, but is preferably 50000 or more, more preferably 80000 or more. These hydrophilic polymers may be used alone or in combination. Moreover, the kind of hydrophilic polymer which comprises a surface hydrophilic layer and a middle hydrophilic layer may be the same, and may differ.

  Both hydrophilic layers of the lithographic printing plate precursor according to the invention both contain an inorganic pigment. As the inorganic pigment, various known inorganic pigment particles such as silica, zinc oxide, titanium oxide, alumina, zirconia, tin oxide, magnesium oxide, antimony oxide, cerium oxide, niobium oxide, barium sulfate, calcium carbonate, and clay can be used. However, it is most preferable to use silica particles. These inorganic pigments may be used in combination, or the same kind of pigment may be used for the surface hydrophilic layer and the middle hydrophilic layer, or another kind of pigment may be used.

  In the present invention, since the hydrophilic layer is preferably provided by applying a coating liquid, the inorganic pigment particles used in the present invention are preferably used in the form of a slurry and mixed with the coating liquid. . The production process of the inorganic pigment particle slurry of the present invention includes a primary dispersion process in which inorganic pigment particles are added to a dispersion medium and mixed (preliminary mixing), and a coarse dispersion obtained in the primary dispersion process is dispersed in a dispersing device (for example, a high-pressure homogenizer). Or a ball mill).

  The preliminary mixing in the primary dispersion step can be performed by ordinary propeller stirring, turbine stirring, homomixer stirring, ultrasonic stirring, or the like. As a dispersion apparatus used in the secondary dispersion step, at least one selected from a high-pressure homogenizer, an ultra-high pressure homogenizer, an ultrasonic disperser, and a thin film-circulating disperser is preferably used. The high-pressure homogenizer is a dispersion machine that uses shearing force when passing the workpiece through the gap between the valve and the valve seat at high pressure and high speed, and is widely known as a gourin type. APV Gourin, Runny, NIRO SOAVI Commercially available from the company, Nippon Seiki Seisakusho, Sanwa Kikai Co., Ltd., and the like. The ultra-high pressure homogenizer is a disperser capable of processing at higher pressures that cannot be achieved with a high-pressure homogenizer, and uses the shearing force and impact force when passing the object to be processed through the narrow and narrow path in the chamber at high pressure and high speed. Sugino Machine Co., Ltd. is known, as well as the opposed collision type jet pulverization type that uses shearing force when the liquids to be treated are jetted at high pressure and high speed from the opposed nozzles to collide with the liquids to be treated. Commercially available products such as Optimizer, Microfluidizer, Nanomizer from Mizuho Industry Co., Ltd., Nanomizer, etc. can be used. The ultrasonic disperser is a disperser using ultrasonic vibration energy generated from an ultrasonic oscillator, and commercially available from Nippon Seiki Seisakusho Co., Ltd. can be used. A thin-film disperser is a type that uses shear stress when a liquid to be treated is introduced into a chamber with a brush and has a high-speed rotation shaft, and the liquid to be treated becomes a thin film and moves up the inner wall of the chamber. Yes, it is possible to use a product marketed under the trade name “Filmix” from Tokushu Kika Kogyo Co., Ltd.

  The dispersion medium of the inorganic pigment particles is mainly composed of water, but may contain a small amount of an organic solvent (a lower alcohol such as ethanol or a low boiling point solvent such as ethyl acetate). In that case, the organic solvent is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total dispersion medium. Various known pH buffering agents such as sodium acetate, borax and sodium hydrogen carbonate can also be added. In addition, a hydrophilic polymer can be used as a dispersion aid.

  About the form of the inorganic pigment particle used for this invention, the form in the stage which slurry manufacture was complete | finished is meant. The shape of the particles can be any shape such as a spherical shape, a needle shape, a feather shape, or an indeterminate shape, and further, these particles can be used as primary particles and can be in the form of their aggregated secondary particles. Among these, the shape of the inorganic pigment particles used in the present invention is preferably a secondary particle in which primary particles are aggregated in a lump, and the primary particles are particles having an average particle diameter of 25 μm or less, and this is a lump aggregate It is preferable that secondary particles are formed. Such silica includes synthetic silica fine particles (hereinafter referred to as gas phase method silica) obtained by a gas phase method disclosed in JP-B-3-56552, JP-A-10-81064 and the like. Vapor phase method silica is commercially available as Aerosil from Nippon Aerosil Co., Ltd. and can be obtained.

  In the present invention, the average particle diameter of the inorganic pigment means the particle diameter of the secondary particles when the pigment forms secondary particles, and the particle diameter of the primary particles when they are not formed. The average particle diameter of the preferable inorganic pigment fine particles in the present invention is preferably 1 μm or less, more preferably 500 nm or less. By using such fine particles, a layer having a preferable porous structure can be formed. The average particle diameter of secondary particles having an average particle diameter of 50 nm or more, or primary particles in the case where secondary particles are not formed and having an average particle diameter of 50 nm or more is also determined by a laser scattering type particle size distribution meter (for example, It can be measured by HORIBA, Ltd., LA920). Smaller particles can be confirmed using an electron microscope. Further, when the particles form secondary particles in which the primary particles are aggregated, the size of the primary particles and the shape of the aggregation can be confirmed using the same electron microscope.

  In the present invention, the inorganic pigment / binder ratio of the surface hydrophilic layer is preferably 2/1 or more, more preferably 3/1 or more in terms of mass ratio. At this ratio, a preferable porous structure having pores of 100 nm or more can be obtained. Whether or not such a preferable porous structure is taken can be measured by applying a hydrophilic layer having the same structure to a non-porous base such as a polyester film and using a gas adsorption method.

In the present invention, the surface hydrophilic layer is an extremely important factor because if the coating amount is too thick, the ink composition is not absorbed up to the middle hydrophilic layer, and if it is too thin, the ink composition cannot be completely absorbed. is there. A preferred coating amount 0.5 g / m ² or less in terms of solid content, more preferably 0.01~0.4g / m ^2, more preferably from 0.05 to 0.3 g / m ^2. Among them, the preferred amount of the inorganic pigment as the main component is 0.02 to 0.4 g / m ² , more preferably 0.06 to 0.25 g / m ² . The amount of the binder used is preferably 0.001 to 0.1 g / m ^2, more preferably a 0.002~0.05g / m ^2.

In the present invention, the inorganic pigment / binder ratio of the middle hydrophilic layer must be smaller than that of the surface hydrophilic layer. However, on the other hand, if the value is too small, the absorptivity of the ink composition is deteriorated and bleeding occurs. A preferable inorganic pigment / binder ratio is 1/1 or more, more preferably 3/2 to 2/1. With such a ratio, a porous structure having pores of 50 to 100 nm can be formed. The amount of the inorganic pigment in the middle hydrophilic layer also 0.05-5 g / m ^2, preferably from 0.1 to 0.4 g / m ^2. The same amount of the binder used 0.025~5g / m ^2, preferably from 0.05 to 0.4 g / m ^2.

  In the present invention, it is preferable to crosslink using a crosslinking agent capable of undergoing a crosslinking reaction with the binder used in both hydrophilic layers so that the hydrophilic layer cannot be removed during printing. Examples of the crosslinking agent include inorganic compounds such as chromium alum, aldehydes such as formalin, glyoxal, malealdehyde, and glutaraldehyde, N-methylal compounds such as urea and ethylene urea, mucochloric acid, and 2,3-dihydroxy. Aldehyde-related compounds such as -1,4-dioxane, active halogens such as 2,4-dichloro-6-hydroxy-S-triazine salt and 2,4-dihydroxy-6-chloro-S-triazine salt Compounds, divinyl sulfone, divinyl ketone, N, N, N-triacryloyl hexahydrotriazine, compounds having two or more active three-membered ethyleneimino groups or epoxy groups in the molecule, isocyanate groups in the molecule Various compounds including two or more compounds, dialdehyde starch as polymer hardener May be used alone or two or more compounds. In addition to these, known cross-linking agents such as the cross-linking agents described in “Chemical Reaction of Polymer” (Nobu Okawara 1972, Chemical Dojinsha), etc. Can be used. Among these crosslinking agents, aldehydes are preferably used. The amount of the crosslinking agent used is 1 to 20% by weight, preferably 5 to 10% by weight, based on the binder.

  Further, in order to coat both hydrophilic layers of the lithographic printing plate precursor according to the present invention, some of anionic, cationic or nonionic surfactants may be used as an auxiliary agent. Especially for surface hydrophilic layers, use of a surfactant that can significantly reduce the surface tension, such as fluorine-containing surfactants or silicon-containing surfactants, to prevent image bleeding, thereby further preventing image bleeding. This is preferable.

  In addition, a matting agent, a thickening agent, an antistatic agent, and the like can be used for both hydrophilic layers of the lithographic printing plate precursor according to the invention. In addition, in order to increase the stability during coating, depending on the type of hydrophilic polymer having a hydroxyl group and its sulfate ester, salts such as potassium nitrate, calcium nitrate, ammonium nitrate, potassium chloride, calcium chloride, and potassium sulfate may be added to form a gelling ability. Can also be increased. Further, coloring materials such as pigments such as carbon black and phthalocyanine blue and dyes such as food blue No. 1, No. 2 and food red No. 3 can be added.

  In the present invention, as a support for a lithographic printing plate precursor, resin-coated paper, synthetic paper, polyester resin such as polyethylene terephthalate, diacetate resin, triacetate resin, acrylic resin, polycarbonate resin, polyvinyl chloride, polyimide resin, cellophane, A synthetic or semi-synthetic polymer film such as celluloid or a metal plate such as aluminum or iron may be used as long as it can withstand lithographic printing. However, in order to achieve the object of the present invention, an inexpensive paper or film base should be used. preferable. In addition, the surface of these supports can be subjected to a surface treatment in order to improve adhesion with a layer to be coated as an upper layer.

In the present invention, the lithographic printing plate precursor may be provided with an undercoat layer under the hydrophilic layer in addition to the hydrophilic layer. In the undercoat layer, a hydrophilic polymer similar to the surface hydrophilic layer and shinshin water total may be used as a binder, and an inorganic pigment similar to the surface hydrophilic layer and shinshin water total may be added. Its preferred amount 0.05-5 g / m ² hydrophilic polymeric binder, more preferably 0.1 to 3 g / m ^2, the inorganic pigment is 0~0.5g / m ^2.

Further, a polymer latex as a water-insoluble polymer can be used as a binder other than the hydrophilic polymer in the undercoat layer. As the polymer latex, various known latexes such as homopolymers and copolymers can be used. Homopolymers include vinyl acetate, vinyl chloride, styrene, methyl acrylate, butyl acrylate, methacrylonitrile, butadiene, and isoprene. Copolymers include ethylene butadiene, styrene butadiene, styrene p-methoxystyrene. , Styrene / vinyl acetate, vinyl acetate / vinyl chloride, vinyl acetate / diethyl maleate, methyl methacrylate / acrylonitrile, methyl methacrylate / butadiene, methyl methacrylate / styrene, methyl methacrylate / vinyl acetate, methyl methacrylate / vinylidene chloride, methyl acrylate / acrylonitrile , Methyl acrylate / butadiene, methyl acrylate / styrene, methyl acrylate / vinyl acetate, acrylic acid / butyl acrylate, methyl Acrylate-vinyl chloride, butyl acrylate-styrene and the like. The average particle size of the polymer latex used in the present invention is preferably 0.01 to 1.0 μm, more preferably 0.05 to 0.8 μm. The preferred amount of polymer latex used is 0 to 0.3 g / m ² in terms of solid content. A preferred inorganic pigment / binder ratio is 0 to 1/2. In addition, various matting agents, antistatic agents, surfactants, crosslinking agents, colorants such as pigments and dyes can be added to the undercoat layer.

  In the present invention, the lithographic printing plate precursor includes a hydrophilic layer and an undercoat layer, as well as a conductive layer, an antistatic layer, an anticurl layer for preventing curling of the support, and a curl promoting layer for imparting a desired curl as necessary. Etc. can be provided.

  In the present invention, a lithographic printing plate is made by imagewise printing an ink composition containing a lipophilic substance with an inkjet printer, and then irradiating the printed lithographic printing plate with ultraviolet rays over the entire surface. Ink jet printers are generally equipped with dedicated ink jet heads depending on whether the ink composition used is water-based, solvent-based, or ultraviolet curable. In the present invention, since the preferred ink jet composition is aqueous, the preferred ink jet printer is an ink jet printer equipped with an aqueous ink jet head.

  The ink composition used in the present invention contains an ultraviolet curable resin, a polymerization initiator, and a diluent, and may further contain a coloring material, a surfactant, and an auxiliary agent.

  As the ultraviolet curable resin used in the ink composition used in the present invention, various known water-based ultraviolet curable resins such as urethane acrylate type, epoxy acrylate type, and polyester acrylate type can be used. Examples of such water-based ultraviolet curable resins include JP-A-3-168209, JP-A-4-21413, JP-A-5-140251, JP-A-7-242716, and JP-A-7-25958. JP-A-7-62026, JP-A-6-287260, JP-A-9-146270, JP-A-5-222135, JP-A-9-136981, JP-A-6-298751, JP-A-7 There are ultraviolet curable resins described in Japanese Patent No. -43900. Particularly preferred UV curable resins are UV curable resins having 3 or more reactive groups in the molecule and a viscosity of 10 mPa · s or more, preferably 50 mPa · s or more, more preferably 100 to 3000. In addition, water-based curable resins are roughly classified into water-soluble UV curable resins, forced emulsification type UV curable resins, and self-emulsifying type UV curable resins. Thereafter, it is difficult to redissolve in the diluent and the head is likely to be clogged, so it is preferable to use a water-soluble cured resin. However, the present inventors have found that the disadvantage can be eliminated by dissolving once with a water-soluble organic solvent such as ethyl alcohol, or a water-soluble UV-curable resin, or a polymerization initiator as a solvent even with a self-emulsifying type UV-curable resin. In general, it is also preferable to dissolve and use a self-emulsifying type ultraviolet curable resin that generally forms a strong film after ultraviolet irradiation.

  The ultraviolet curable resins in the ink composition used in the present invention can be used alone or in combination of a plurality of types, but it is particularly preferable to use a mixture of a water-soluble ultraviolet resin and a self-emulsifying ultraviolet curable resin. The preferred mixing ratio is 10: 1 to 1: 2, preferably 5: 1 to 1: 1, by mass ratio of the solid content. Moreover, the density | concentration of the total ultraviolet curable resin in an ink composition is 1-40 mass%, More preferably, it is 5-30%.

  The ink composition used in the present invention contains a photopolymerization initiator. When high-energy rays such as electron beams are used as active energy rays instead of ultraviolet rays, it is possible to create an image with sufficient strength to be printed without a photopolymerization initiator, but it is safe and simple. It is preferable to use ultraviolet rays. Therefore, the ink composition used in the present invention contains a photopolymerization initiator and is irradiated with ultraviolet rays after printing to fix the image.

  As a photopolymerization initiator, it is soluble in water, the surface tension adjusting agent used in the present invention, a water-soluble organic solvent, is stably present in ink, and radicals generated by ultraviolet rays are unsaturated double bonds and efficiency. Anything that reacts automatically can be used. Specifically, benzoin compounds such as benzoin ethyl ether and benzoin isopropyl ether, 2-hydroxy-2methyl-1-phenylpropan-1-one, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2 Examples thereof include acetophenone compounds such as -propyl) ketone, benzophenone compounds such as benzophenone, and thioxanthone compounds, but are not limited to these, and two or more kinds may be used in combination. The usage-amount of these photoinitiators shall be 0.1-20 mass% with respect to ultraviolet curable resin. Photoinitiators such as triethanolamine and methyldiethanolamine can also be used.

  In the ink composition used in the present invention, a diluent is used to adjust the viscosity. In an ink jet printer, particularly an aqueous ink jet printer, the head is clogged with an ink composition having a high viscosity. Therefore, the viscosity is preferably 15 mPa · s or less, more preferably 10 mPa · s or less, and further preferably 2 to 5 mPa · s. In order to obtain such a preferable viscosity, a diluent is used because it is impossible with only an ultraviolet curable resin or a polymerization initiator. As the diluent, water is most preferable from the viewpoint of the environment, but when water alone cannot completely dissolve the ultraviolet curable resin, it is preferable to use ethanol. Furthermore, other known water-soluble organic solvents can also be used. Specific examples thereof include glycols such as ethylene glycol, diethylene glycol, polyethylene glycol, glycerin, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, glycol ethers such as ethylene glycol monophenyl ether, N- Examples include pyrrolidones such as methyl-2-pyrrolidone, alkanolamines such as triethanolamine, alcohols such as methanol and isopropyl alcohol, and dimethyl sulfoxide. If the solvent remains at the time of ultraviolet exposure, the image strength is lowered. Therefore, it is preferable to use an organic solvent having a boiling point of 100 ° C. or lower. As a usage-amount of a diluent, water is 0-50 mass%, Preferably it is 2-20 mass%, and 30-90 mass% is preferable with a diluent in combination with another organic solvent.

  The ink composition used in the present invention preferably contains a color material for plate inspection after printing. As the coloring material, dyes and pigments generally used in ink jet recording inks can be used. Examples of the dye include azo dyes as direct dyes, phthalocyanine dyes, azo dyes as acidic dyes, and anthraquinone dyes. As the pigment, all conventionally known organic pigments and inorganic pigments can be used. Specific examples include organic pigments such as azo pigments, phthalocyanine pigments, perylene pigments, quinacridone pigments, isoindoline pigments, and inorganic pigments such as titanium oxide and carbon black, but are not limited thereto.

  These color materials can be used alone or in combination. The content of the color material in the ink composition is preferably in the range of 0.1 to 10% by mass in order to obtain good film strength and colorability.

  The ink composition used in the present invention may contain a surfactant as a surface tension adjusting agent. As the surfactant, silicone-based, fluorine-based, acrylic-based, and acetylenic diol-based surfactants generally used in water-based paints and inks can be used.

  In addition, the ink composition used in the present invention may contain auxiliary agents contained in known ink compositions. As auxiliary agents, alkali metal hydroxides, pH adjusters such as alkanolamines, antibacterial and antifungal agents, sequestering agents, pigment dispersants, water-soluble resins, and the like may be used.

  In the present invention, after printing with an ink jet printer, the image is irradiated with ultraviolet rays to cure the image. The ultraviolet irradiation may be performed during printing or after printing. For example, as described in JP-A No. 2004-322560, an ultraviolet lamp may be provided right next to the inkjet head, or as described in JP-A No. 2000-186243. As described above, an ultraviolet lamp may be attached to the exit portion of the ink jet printer, or a known ultraviolet irradiation device independent of the printer may be used. However, use of an ultraviolet irradiation device that is independent of the printer to prevent the ink attached to the inkjet head from being cured by stray light because the intensity of the image is stronger when the diluent is evaporated and the ultraviolet rays are irradiated. Is preferred. Therefore, it is preferable that the time from the printing to the irradiation with ultraviolet rays is preferably from several seconds to several minutes. In addition, after printing, the lithographic printing plate can be passed through a dryer before irradiation with ultraviolet rays to accelerate the drying of the diluent. However, application of temperature is preferable because the viscosity of the ultraviolet curable resin decreases and the resin moves. Is dried by applying air of 50 ° C. or less.

  As the ultraviolet lamp used in the ultraviolet irradiation apparatus, a so-called low-pressure mercury lamp whose mercury vapor pressure is 1 to 10 Pa during lighting, a high-pressure mercury lamp having a higher pressure, a mercury lamp coated with a phosphor, or the like Is preferred. The emission spectrum of these mercury lamps in the ultraviolet region is in the range of 184 nm to 450 nm, which is suitable for efficiently reacting the ultraviolet polymerizable compound in the black or colored ink. Moreover, since a small power supply can be used, it is suitable also in that sense. As mercury lamps, metal halide lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, xenon flash lamps, deep UV lamps, UV lasers, etc. have been put into practical use, and the emission wavelength range includes the above range, so the power supply size, input intensity, It can be appropriately selected and used according to the lamp shape and the like. The light source is preferably selected in consideration of suitability with the photopolymerization initiator to be used.

The necessary ultraviolet intensity is preferably about ² to 50 mW / cm ^{2 in the} total energy of the ultraviolet part in order to obtain a better heavy speed. Since the printable intensity cannot be obtained if the integrated irradiation amount is insufficient, it is preferable to perform the irradiation process in consideration of the necessary integrated irradiation amount.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but it is needless to say that the present invention is not limited by this description.

<Example 1>
Aerosil 300 (gas phase method silica manufactured by Tokuyama Corporation) (1.44 kg) was added to an aqueous solution containing 14.4 g of sodium hydroxide and 6.12 g of sodium acetate to make a total amount of 8 kg. This was stirred with a sawtooth blade type disperser at a blade peripheral speed of 30 m / sec for 90 minutes to obtain an 18% by mass silica coarse dispersion. The silica coarse dispersion obtained in the primary dispersion step was emulsified and dispersed three times with a high pressure homogenizer under the conditions of a throughput of 40 l / hour and a pressure of 200 kg / cm ² to obtain a silica dispersion. The obtained dispersion was stored at 60 ° C. for 1 hour with a propeller blade-type disperser while stirring at low speed to obtain a silica slurry. When the particle diameter in the obtained slurry was examined using a laser scattering particle size distribution analyzer HORIBA LA920, the secondary particle diameter was 0.1 μm. Further, when observed with an electron microscope, it was an aggregate in which primary particles having a primary particle diameter of 12 nm were aggregated in a lump.

  The hydrophilic layer containing the silica slurry was applied to both sides of the PET base according to the following formulation. As a result of measuring the pore diameter distribution of 1 g of the obtained sample using a specific surface area measuring device SA3100 (manufactured by Beckman Cole Counter Co., Ltd.), the results are shown in Table 1.

<Hydrophilic prescription A / 1 m ² (one side)>
Aerosil 300 (solid content) 1.89g
κ Carrageenan 0.51g
Glyoxal (37% aqueous solution) 0.02 g
Activator (coating aid) 1g

<Hydrophilic prescription B / 1m ² (one side)>
Aerosil 300 (solid content) 1.85 g
Glyoxal (37% aqueous solution) 0.02 g
κ Carrageenan 0.55g
Activator (coating aid) 1g

<Hydrophilic prescription C / 1m ² (one side)>
Aerosil 300 (solid content) 1.66 g
Glyoxal (37% aqueous solution) 0.02 g
κ Carrageenan 0.74g
Activator (coating aid) 1g

<Hydrophilic prescription D / 1m ² (one side)>
Aerosil 300 (solid content) 1.55g
Glyoxal (37% aqueous solution) 0.02 g
κ Carrageenan 0.85g
Activator (coating aid) 1g

<Hydrophilic prescription E / 1 m ² (one side)>
Aerosil 300 (solid content) 1.5g
Glyoxal (37% aqueous solution) 0.02 g
κ Carrageenan 0.9g
Activator (coating aid) 1g

<Hydrophilic prescription F / 1 m ² (one side)>
Aerosil 300 (solid content) 1.33g
Glyoxal (37% aqueous solution) 0.02 g
κ Carrageenan 1.07g
Activator (coating aid) 1g

<Hydrophilic prescription G / 1m ² (one side)>
Aerosil 300 (solid content) 1.03g
Glyoxal (37% aqueous solution) 0.02 g
κ Carrageenan 1.37g
Activator (coating aid) 1g

After 135 g / m ² double-sided polyethylene-coated paper (RC paper) was corona discharge processed, an undercoat layer was then applied according to the formulation shown below.

(Undercoat layer prescription / per 1m ² )
κ Carrageenan 0.36g
PA 9281 (Nihon A & L Co., Ltd., SBR latex) 3g
Glyoxal (37% aqueous solution) 0.01g
Activator (coating aid) 1g

The hydrophilic layer containing the above-mentioned silica slurry was applied on the undercoat layer at the coating amount (in solid content) as shown in Table 2 to obtain lithographic printing plate precursors 1-17. In addition, Surflon S-132 (manufactured by Seimi Chemical Co., Ltd., fluorine-containing surfactant) was further added to the surface hydrophilic layer at 20 mg / m ² .

An ink for an ink jet printer was prepared according to the following formulation, and this was put into a black ink of PM-750C (manufactured by Seiko Epson Corp.) and printed on the prepared lithographic printing plate precursor. After printing, the printed part was exposed for 15 seconds with a high-pressure mercury lamp (80 W / cm ² , power supply 1 kW) and cured.

<Ink composition for inkjet printer>
Beam set AQ9 (Arakawa Chemical Industries, Ltd., water-soluble type, viscosity 1500 mPa · s, reactive groups 2 to 3) 12.5 g
Beam set EM90 (Arakawa Chemical Industries, Ltd., self-emulsifying 40% aqueous dispersion, viscosity 100 mPa · s, reactive groups 6-9) 12.5 g
Food Blue No.1 0.1g
Darocur 1173 (Ciba Specialty Chemicals Co., Ltd.) 2g
Ethanol 58g
Dissolve completely with ethanol, and then add water to bring the total volume to 100 g.

  Using the obtained printing plate, printing was performed with an offset printing machine (3200CD manufactured by Ryobi Imaging Co., Ltd.).

The soiled state and printing durability of the printed material were evaluated according to the following criteria.
<Evaluation of dirt on printed matter>
1: Not dirty at all.
2: Partially dirty.
3: The entire surface is thin and dirty.
4: The entire surface is dirty.
<Evaluation of printing durability of printed matter>
1: Print image does not change at all.
2: The printed image is hardly changed, but the fine line image is slightly thinned.
3: Slightly lower ink density in the image area.
4: The ink density in the image area is lowered and the thin line portion is thinned.

The moisturizing liquid and ink used for evaluating the soiled state and printing durability of the printed material are shown below.
<Evaluation of dirt>
1: Moisturizer Nitro Chemical Co., Ltd. Astro Mark III 1% (Use water supply to make 1%.)
2: Ink Dai Nippon Ink Chemical Co., Ltd. New Champion Purple 68N
<Evaluation of printing durability>
1: Dampening solution Mitsubishi Paper Industries SLM-OD30 3% (Use water supply to make 3%.)
2: Ink Dai Nippon Ink Chemical Co., Ltd. New Champion Ink 85H
The dirt state was evaluated based on the dirt state of the 1000th blanket. The printing durability was evaluated in a state where the fine line image part (50 micron fine line) of the printed material after 10,000 sheets were printed was thin and the density of the image part was lowered. In addition, the 100th printed matter in the printing durability test was visually observed for the image blur, and “O” indicates that there is no blur, “Δ” indicates that it is generated, and “X” indicates that the blur is generated. These results are shown in Table 3.

  From the above results, it can be seen that when the surface hydrophilic layer has an inorganic pigment / binder ratio larger than that of the medium hydrophilic layer, good results can be obtained in all of the printing durability, smudge and image bleeding. Further, it can be seen that the printing durability deteriorates when the coating amount of the surface hydrophilic layer becomes 0.6 g. Moreover, the higher the inorganic pigment / binder ratio of the surface hydrophilic layer is, the better, and those exceeding 3 indicate good results. Further, the medium hydrophilic layer is also preferably porous rather than nonporous, and it can be seen that better results can be obtained when the inorganic pigment / binder ratio is about 3/2 to 2/1.

<Example 2>
While stirring an aqueous solution containing 14.4 g of sodium hydroxide and 6.12 g of sodium acetate in a 20 l beaker, precipitated silica (Nipseal LB, Tosoh Silica Co., Ltd.) having an initial secondary particle size of 17 μm. 1.44 kg was added to make the total amount 8 kg, and a primary dispersion was prepared. Next, a pulverizer, 15MR type homogenizer manufactured by GALIN was operated under the conditions of a throughput of 40 l / h and a pressure of 200 kg / cm ² to obtain a secondary dispersion in two passes. When the particle diameter in the obtained slurry was examined for the secondary particle diameter using a laser scattering particle size distribution analyzer HORIBA LA920, it was 0.5 μm. When observed with an electron microscope, the particles were 0.5 μm in size.

The obtained silica dispersion was applied as a middle hydrophilic layer on the substrate coated with the undercoat layer used in Example 1 according to the following formulation, and the surface hydrophilic layer used in the planographic printing plate No1 of Example 1 ( A formulation obtained by adding Surflon S132 to formulation A, a coating amount of 0.1 g / m ² ), was applied in the same manner as in Example 1 to prepare a lithographic printing plate 18.

<Medium hydrophilic layer prescription H / per 1 m ² >
κ Carrageenan 0.15g
Nip seal LB (in solid content) 0.25g
Glyoxal (37% aqueous solution) 0.005 g
Surfactant (coating aid) 0.05g

Furthermore, water was added so that the inorganic pigment described in the following middle hydrophilic layer formulas I to L was 10% by mass, and the mixture was dispersed with an ultrasonic cleaner for 5 minutes to prepare an inorganic pigment dispersion. A layer coating solution was prepared. Similarly to the planographic printing plate 18, each of the intermediate hydrophilic layers I to L and the surface hydrophilic layer (preparation A plus Surflon S132, coating amount 0.1 g / m ² ) are applied on the undercoated support. Plate making was carried out in the same manner as in Example 1 to prepare lithographic printing plates 19-22.

<Medium hydrophilic layer prescription I per 1 m ² >
κ Carrageenan 0.15g
Silicia 310 (Fuji Silysia Chemical Co., Ltd., non-aggregated primary particles with an average particle size of 1.4 μm) 0.25 g
Glyoxal (37% aqueous solution) 0.005 g
Surfactant (coating aid) 0.05g

<Medium hydrophilic layer formulation J / 1m ² >
κ Carrageenan 0.15g
Silicia 770 (Fuji Silysia Chemical Co., Ltd., non-aggregated primary particles with an average particle size of 6 μm)
0.25g
Glyoxal (37% aqueous solution) 0.005 g
Surfactant (coating aid) 0.05g

<Medium hydrophilic layer prescription K / 1m ² >
κ Carrageenan 0.15g
Barium sulfate B-1 (manufactured by Sakai Chemical Industry Co., Ltd., non-aggregated primary particles having an average particle diameter of 0.8 μm)
0.25g
Glyoxal (37% aqueous solution) 0.005 g
Surfactant (coating aid) 0.05g

<Medium hydrophilic layer formulation L / 1 m ² >
κ Carrageenan 0.15g
Barium sulfate B-54 (manufactured by Sakai Chemical Industry Co., Ltd., non-aggregated primary particles having an average particle size of 1.2 μm)
0.25g
Glyoxal (37% aqueous solution) 0.005 g
Surfactant (coating aid) 0.05g

  The obtained lithographic printing plates 18 to 22 were evaluated in the same manner as in Example 1, and the results are shown in Table 4.

  It can be seen from Table 4 that the blurring is particularly bad when the average particle diameter is not less than 1 μm regardless of the kind of the inorganic pigment.

<Example 3>
Using the planographic printing plates 1 and 2 produced in Example 1, an image is printed with black ink of a UV printer UJF-604 (Mimaki Co., Ltd., equipped with a UV irradiation device next to an inkjet head). When evaluated in the same manner as in No. 1, printing durability and stain were evaluated as No. 1 and no bleeding was obtained. Although the printer is expensive, it has been found that good results can be obtained using a non-aqueous UV inkjet printer.

<Example 4>
A germicidal lamp (GL10, manufactured by Toshiba Corporation) was used as the ultraviolet light source instead of a high-pressure mercury lamp, and the same procedure as in Example 1 was performed except that the distance between the plate and the light source was 2 cm and the exposure time was 5 minutes. 1 was obtained. In the present invention, even if it takes time until the ultraviolet curable resin is cured, image blurring does not occur. Therefore, it is possible to use a simple curing apparatus that takes time to give sufficient energy to cure the ultraviolet curable resin. Thus, the usefulness of the present invention can be understood.

Claims (7)

  In a lithographic printing plate having a hydrophilic layer provided on a support, the hydrophilic layer has at least two continuous layers, the hydrophilic layer contains an inorganic pigment having an average particle diameter of 1 μm or less, and is close to the support A lithographic printing plate precursor wherein the inorganic pigment / binder ratio of the layer is smaller than that of the layer farther from the support.   2. The lithographic printing plate precursor as claimed in claim 1, wherein the hydrophilic pigment / binder ratio of the hydrophilic layer farther from the support is 2/1 or more. The lithographic printing plate precursor as claimed in claim 1 or 2, wherein the coating amount of the hydrophilic layer farther from the support is 0.5 g / m ² or less in terms of solid content.   The lithographic printing plate precursor as claimed in any one of claims 1 to 3, wherein an inorganic pigment / binder ratio of the hydrophilic layer closer to the support is 1/1 or more.   A lithographic printing plate making method, comprising: printing an ink composition containing an oleophilic substance on a lithographic printing plate precursor according to any one of claims 1 to 4 by an inkjet method.   6. The method for making a lithographic printing plate according to claim 5, wherein the lipophilic substance is ultraviolet curable.   The lithographic printing plate making method according to claim 5 or 6, wherein the ink composition contains water or ethyl alcohol.